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Table 1 Selection and enrollment status of Cape Cod, Massachusetts women contributing at least one index pregnancy, by initial exposure status [N (%)]

From: Prenatal drinking-water exposure to tetrachloroethylene and ischemic placental disease: a retrospective cohort study

  

Initial exposure statusa

 

Exposedb

Unexposedc

Total

Selected

1,492

1,704

3,196

Excluded during enrollment

   

  Never located

132 (8.8)

136 (8.0)

268 (8.4)

  No response

245 (16.4)

336 (19.7)

581 (18.2)

  Ineligible

7 (0.5)

8 (0.5)

15 (0.5)

  Refusal

149 (10.0)

137 (8.0)

286 (8.9)

Returned questionnaire

   

  Percent of located

959 (70.5)

1,087 (69.3)

2,046 (69.9)

  Percent of selected

959 (64.3)

1,087 (63.8)

2,046 (64.0)

Excluded during exposure assessment and analysis

   

  Incalculable exposure—insufficient data for geocoding residential address

60 (6.3)

75 (6.9)

135 (6.6)

  Incalculable exposure-missing data on LMP

20 (2.1)

21 (1.9)

41 (2.0)

  Multiple birth

11 (1.2)

21 (1.9)

32 (1.6)

  Birth anomaly

22 (2.3)

32 (2.9)

54 (2.6)

  Missing data on key covariates

9 (0.9)

9 (0.8)d

18 (0.9)

Final sample

834

932

1,766

  1. Abbreviation: LMP last menstrual period.
  2. aThe exposure status of each pregnancy was assessed later (see Methods).
  3. bContributed ≥1 exposed index births.
  4. cContributed no exposed index births.
  5. dOne woman contributed a stillbirth only to the final analyses.